There is a sign in the concourse advising no baggage check-in before 2 hours before departure time, which I suspect is recent.
Perhaps the rule was originally airline specific - I know it applied when I flew to IOM with Euromanx (from 2005 I think), VLM, Aer Arran and latterly BA. I believe it was also in place for British European flights.
Or maybe they know you and gave you special treatment….?